On the Omni/Omni Pro systems, you must use a 1K ohm end-of-line resistor for each zone input. With the Omni LT, Omni LTe Omni II, Omni IIe, and Omni Pro II, Lumina, and Lumina Pro, resistors are optional, with three exceptions:

All fire devices (smoke, heat, and gas detectors) must be wired normally open, with a 1K resistor installed.

All zones used on the 17A00 Expansion Enclosure (used on Omni Pro II controllers) require resistors.

If any normally open devices are used on the controller and/or hardwire expander, then resistors must be set to yes and used on all zones